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//! A different sort of visitor for walking fn bodies. Unlike the
//! normal visitor, which just walks the entire body in one shot, the
//! `ExprUseVisitor` determines how expressions are being used.
pub use self::LoanCause::*;
pub use self::ConsumeMode::*;
pub use self::MoveReason::*;
pub use self::MatchMode::*;
use self::TrackMatchMode::*;
use self::OverloadedCallType::*;
use crate::hir::def::{CtorOf, Res, DefKind};
use crate::hir::def_id::DefId;
use crate::hir::ptr::P;
use crate::infer::InferCtxt;
use crate::middle::mem_categorization as mc;
use crate::middle::region;
use crate::ty::{self, DefIdTree, TyCtxt, adjustment};
use crate::hir::{self, PatKind};
use std::rc::Rc;
use syntax_pos::Span;
use crate::util::nodemap::ItemLocalSet;
///////////////////////////////////////////////////////////////////////////
// The Delegate trait
/// This trait defines the callbacks you can expect to receive when
/// employing the ExprUseVisitor.
pub trait Delegate<'tcx> {
// The value found at `cmt` is either copied or moved, depending
// on mode.
fn consume(&mut self,
consume_id: hir::HirId,
consume_span: Span,
cmt: &mc::cmt_<'tcx>,
mode: ConsumeMode);
// The value found at `cmt` has been determined to match the
// pattern binding `matched_pat`, and its subparts are being
// copied or moved depending on `mode`. Note that `matched_pat`
// is called on all variant/structs in the pattern (i.e., the
// interior nodes of the pattern's tree structure) while
// consume_pat is called on the binding identifiers in the pattern
// (which are leaves of the pattern's tree structure).
//
// Note that variants/structs and identifiers are disjoint; thus
// `matched_pat` and `consume_pat` are never both called on the
// same input pattern structure (though of `consume_pat` can be
// called on a subpart of an input passed to `matched_pat).
fn matched_pat(&mut self,
matched_pat: &hir::Pat,
cmt: &mc::cmt_<'tcx>,
mode: MatchMode);
// The value found at `cmt` is either copied or moved via the
// pattern binding `consume_pat`, depending on mode.
fn consume_pat(&mut self,
consume_pat: &hir::Pat,
cmt: &mc::cmt_<'tcx>,
mode: ConsumeMode);
// The value found at `borrow` is being borrowed at the point
// `borrow_id` for the region `loan_region` with kind `bk`.
fn borrow(&mut self,
borrow_id: hir::HirId,
borrow_span: Span,
cmt: &mc::cmt_<'tcx>,
loan_region: ty::Region<'tcx>,
bk: ty::BorrowKind,
loan_cause: LoanCause);
// The local variable `id` is declared but not initialized.
fn decl_without_init(&mut self,
id: hir::HirId,
span: Span);
// The path at `cmt` is being assigned to.
fn mutate(&mut self,
assignment_id: hir::HirId,
assignment_span: Span,
assignee_cmt: &mc::cmt_<'tcx>,
mode: MutateMode);
// A nested closure or generator - only one layer deep.
fn nested_body(&mut self, _body_id: hir::BodyId) {}
}
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum LoanCause {
ClosureCapture(Span),
AddrOf,
AutoRef,
AutoUnsafe,
RefBinding,
OverloadedOperator,
ClosureInvocation,
ForLoop,
MatchDiscriminant
}
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum ConsumeMode {
Copy, // reference to x where x has a type that copies
Move(MoveReason), // reference to x where x has a type that moves
}
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum MoveReason {
DirectRefMove,
PatBindingMove,
CaptureMove,
}
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum MatchMode {
NonBindingMatch,
BorrowingMatch,
CopyingMatch,
MovingMatch,
}
#[derive(Copy, Clone, PartialEq, Debug)]
enum TrackMatchMode {
Unknown,
Definite(MatchMode),
Conflicting,
}
impl TrackMatchMode {
// Builds up the whole match mode for a pattern from its constituent
// parts. The lattice looks like this:
//
// Conflicting
// / \
// / \
// Borrowing Moving
// \ /
// \ /
// Copying
// |
// NonBinding
// |
// Unknown
//
// examples:
//
// * `(_, some_int)` pattern is Copying, since
// NonBinding + Copying => Copying
//
// * `(some_int, some_box)` pattern is Moving, since
// Copying + Moving => Moving
//
// * `(ref x, some_box)` pattern is Conflicting, since
// Borrowing + Moving => Conflicting
//
// Note that the `Unknown` and `Conflicting` states are
// represented separately from the other more interesting
// `Definite` states, which simplifies logic here somewhat.
fn lub(&mut self, mode: MatchMode) {
*self = match (*self, mode) {
// Note that clause order below is very significant.
(Unknown, new) => Definite(new),
(Definite(old), new) if old == new => Definite(old),
(Definite(old), NonBindingMatch) => Definite(old),
(Definite(NonBindingMatch), new) => Definite(new),
(Definite(old), CopyingMatch) => Definite(old),
(Definite(CopyingMatch), new) => Definite(new),
(Definite(_), _) => Conflicting,
(Conflicting, _) => *self,
};
}
fn match_mode(&self) -> MatchMode {
match *self {
Unknown => NonBindingMatch,
Definite(mode) => mode,
Conflicting => {
// Conservatively return MovingMatch to let the
// compiler continue to make progress.
MovingMatch
}
}
}
}
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum MutateMode {
Init,
JustWrite, // x = y
WriteAndRead, // x += y
}
#[derive(Copy, Clone)]
enum OverloadedCallType {
FnOverloadedCall,
FnMutOverloadedCall,
FnOnceOverloadedCall,
}
impl OverloadedCallType {
fn from_trait_id(tcx: TyCtxt<'_>, trait_id: DefId) -> OverloadedCallType {
for &(maybe_function_trait, overloaded_call_type) in &[
(tcx.lang_items().fn_once_trait(), FnOnceOverloadedCall),
(tcx.lang_items().fn_mut_trait(), FnMutOverloadedCall),
(tcx.lang_items().fn_trait(), FnOverloadedCall)
] {
match maybe_function_trait {
Some(function_trait) if function_trait == trait_id => {
return overloaded_call_type
}
_ => continue,
}
}
bug!("overloaded call didn't map to known function trait")
}
fn from_method_id(tcx: TyCtxt<'_>, method_id: DefId) -> OverloadedCallType {
let method = tcx.associated_item(method_id);
OverloadedCallType::from_trait_id(tcx, method.container.id())
}
}
///////////////////////////////////////////////////////////////////////////
// The ExprUseVisitor type
//
// This is the code that actually walks the tree.
pub struct ExprUseVisitor<'a, 'tcx> {
mc: mc::MemCategorizationContext<'a, 'tcx>,
delegate: &'a mut dyn Delegate<'tcx>,
param_env: ty::ParamEnv<'tcx>,
}
// If the MC results in an error, it's because the type check
// failed (or will fail, when the error is uncovered and reported
// during writeback). In this case, we just ignore this part of the
// code.
//
// Note that this macro appears similar to try!(), but, unlike try!(),
// it does not propagate the error.
macro_rules! return_if_err {
($inp: expr) => (
match $inp {
Ok(v) => v,
Err(()) => {
debug!("mc reported err");
return
}
}
)
}
impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
/// Creates the ExprUseVisitor, configuring it with the various options provided:
///
/// - `delegate` -- who receives the callbacks
/// - `param_env` --- parameter environment for trait lookups (esp. pertaining to `Copy`)
/// - `region_scope_tree` --- region scope tree for the code being analyzed
/// - `tables` --- typeck results for the code being analyzed
/// - `rvalue_promotable_map` --- if you care about rvalue promotion, then provide
/// the map here (it can be computed with `tcx.rvalue_promotable_map(def_id)`).
/// `None` means that rvalues will be given more conservative lifetimes.
///
/// See also `with_infer`, which is used *during* typeck.
pub fn new(
delegate: &'a mut (dyn Delegate<'tcx> + 'a),
tcx: TyCtxt<'tcx>,
body_owner: DefId,
param_env: ty::ParamEnv<'tcx>,
region_scope_tree: &'a region::ScopeTree,
tables: &'a ty::TypeckTables<'tcx>,
rvalue_promotable_map: Option<&'tcx ItemLocalSet>,
) -> Self {
ExprUseVisitor {
mc: mc::MemCategorizationContext::new(tcx,
param_env,
body_owner,
region_scope_tree,
tables,
rvalue_promotable_map),
delegate,
param_env,
}
}
}
impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
pub fn with_infer(
delegate: &'a mut (dyn Delegate<'tcx> + 'a),
infcx: &'a InferCtxt<'a, 'tcx>,
body_owner: DefId,
param_env: ty::ParamEnv<'tcx>,
region_scope_tree: &'a region::ScopeTree,
tables: &'a ty::TypeckTables<'tcx>,
) -> Self {
ExprUseVisitor {
mc: mc::MemCategorizationContext::with_infer(
infcx,
param_env,
body_owner,
region_scope_tree,
tables,
),
delegate,
param_env,
}
}
pub fn consume_body(&mut self, body: &hir::Body) {
debug!("consume_body(body={:?})", body);
for param in &body.params {
let param_ty = return_if_err!(self.mc.pat_ty_adjusted(&param.pat));
debug!("consume_body: param_ty = {:?}", param_ty);
let fn_body_scope_r =
self.tcx().mk_region(ty::ReScope(
region::Scope {
id: body.value.hir_id.local_id,
data: region::ScopeData::Node
}));
let param_cmt = Rc::new(self.mc.cat_rvalue(
param.hir_id,
param.pat.span,
fn_body_scope_r, // Parameters live only as long as the fn body.
param_ty));
self.walk_irrefutable_pat(param_cmt, &param.pat);
}
self.consume_expr(&body.value);
}
fn tcx(&self) -> TyCtxt<'tcx> {
self.mc.tcx
}
fn delegate_consume(&mut self,
consume_id: hir::HirId,
consume_span: Span,
cmt: &mc::cmt_<'tcx>) {
debug!("delegate_consume(consume_id={}, cmt={:?})",
consume_id, cmt);
let mode = copy_or_move(&self.mc, self.param_env, cmt, DirectRefMove);
self.delegate.consume(consume_id, consume_span, cmt, mode);
}
fn consume_exprs(&mut self, exprs: &[hir::Expr]) {
for expr in exprs {
self.consume_expr(&expr);
}
}
pub fn consume_expr(&mut self, expr: &hir::Expr) {
debug!("consume_expr(expr={:?})", expr);
let cmt = return_if_err!(self.mc.cat_expr(expr));
self.delegate_consume(expr.hir_id, expr.span, &cmt);
self.walk_expr(expr);
}
fn mutate_expr(&mut self,
span: Span,
assignment_expr: &hir::Expr,
expr: &hir::Expr,
mode: MutateMode) {
let cmt = return_if_err!(self.mc.cat_expr(expr));
self.delegate.mutate(assignment_expr.hir_id, span, &cmt, mode);
self.walk_expr(expr);
}
fn borrow_expr(&mut self,
expr: &hir::Expr,
r: ty::Region<'tcx>,
bk: ty::BorrowKind,
cause: LoanCause) {
debug!("borrow_expr(expr={:?}, r={:?}, bk={:?})",
expr, r, bk);
let cmt = return_if_err!(self.mc.cat_expr(expr));
self.delegate.borrow(expr.hir_id, expr.span, &cmt, r, bk, cause);
self.walk_expr(expr)
}
fn select_from_expr(&mut self, expr: &hir::Expr) {
self.walk_expr(expr)
}
pub fn walk_expr(&mut self, expr: &hir::Expr) {
debug!("walk_expr(expr={:?})", expr);
self.walk_adjustment(expr);
match expr.node {
hir::ExprKind::Path(_) => { }
hir::ExprKind::Type(ref subexpr, _) => {
self.walk_expr(&subexpr)
}
hir::ExprKind::Unary(hir::UnDeref, ref base) => { // *base
self.select_from_expr(&base);
}
hir::ExprKind::Field(ref base, _) => { // base.f
self.select_from_expr(&base);
}
hir::ExprKind::Index(ref lhs, ref rhs) => { // lhs[rhs]
self.select_from_expr(&lhs);
self.consume_expr(&rhs);
}
hir::ExprKind::Call(ref callee, ref args) => { // callee(args)
self.walk_callee(expr, &callee);
self.consume_exprs(args);
}
hir::ExprKind::MethodCall(.., ref args) => { // callee.m(args)
self.consume_exprs(args);
}
hir::ExprKind::Struct(_, ref fields, ref opt_with) => {
self.walk_struct_expr(fields, opt_with);
}
hir::ExprKind::Tup(ref exprs) => {
self.consume_exprs(exprs);
}
hir::ExprKind::Match(ref discr, ref arms, _) => {
let discr_cmt = Rc::new(return_if_err!(self.mc.cat_expr(&discr)));
let r = self.tcx().lifetimes.re_empty;
self.borrow_expr(&discr, r, ty::ImmBorrow, MatchDiscriminant);
// treatment of the discriminant is handled while walking the arms.
for arm in arms {
let mode = self.arm_move_mode(discr_cmt.clone(), arm);
let mode = mode.match_mode();
self.walk_arm(discr_cmt.clone(), arm, mode);
}
}
hir::ExprKind::Array(ref exprs) => {
self.consume_exprs(exprs);
}
hir::ExprKind::AddrOf(m, ref base) => { // &base
// make sure that the thing we are pointing out stays valid
// for the lifetime `scope_r` of the resulting ptr:
let expr_ty = return_if_err!(self.mc.expr_ty(expr));
if let ty::Ref(r, _, _) = expr_ty.sty {
let bk = ty::BorrowKind::from_mutbl(m);
self.borrow_expr(&base, r, bk, AddrOf);
}
}
hir::ExprKind::InlineAsm(ref ia, ref outputs, ref inputs) => {
for (o, output) in ia.outputs.iter().zip(outputs) {
if o.is_indirect {
self.consume_expr(output);
} else {
self.mutate_expr(
output.span,
expr,
output,
if o.is_rw {
MutateMode::WriteAndRead
} else {
MutateMode::JustWrite
},
);
}
}
self.consume_exprs(inputs);
}
hir::ExprKind::Continue(..) |
hir::ExprKind::Lit(..) |
hir::ExprKind::Err => {}
hir::ExprKind::Loop(ref blk, _, _) => {
self.walk_block(&blk);
}
hir::ExprKind::Unary(_, ref lhs) => {
self.consume_expr(&lhs);
}
hir::ExprKind::Binary(_, ref lhs, ref rhs) => {
self.consume_expr(&lhs);
self.consume_expr(&rhs);
}
hir::ExprKind::Block(ref blk, _) => {
self.walk_block(&blk);
}
hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => {
if let Some(ref expr) = *opt_expr {
self.consume_expr(&expr);
}
}
hir::ExprKind::Assign(ref lhs, ref rhs) => {
self.mutate_expr(expr.span, expr, &lhs, MutateMode::JustWrite);
self.consume_expr(&rhs);
}
hir::ExprKind::Cast(ref base, _) => {
self.consume_expr(&base);
}
hir::ExprKind::DropTemps(ref expr) => {
self.consume_expr(&expr);
}
hir::ExprKind::AssignOp(_, ref lhs, ref rhs) => {
if self.mc.tables.is_method_call(expr) {
self.consume_expr(lhs);
} else {
self.mutate_expr(expr.span, expr, &lhs, MutateMode::WriteAndRead);
}
self.consume_expr(&rhs);
}
hir::ExprKind::Repeat(ref base, _) => {
self.consume_expr(&base);
}
hir::ExprKind::Closure(_, _, body_id, fn_decl_span, _) => {
self.delegate.nested_body(body_id);
self.walk_captures(expr, fn_decl_span);
}
hir::ExprKind::Box(ref base) => {
self.consume_expr(&base);
}
hir::ExprKind::Yield(ref value, _) => {
self.consume_expr(&value);
}
}
}
fn walk_callee(&mut self, call: &hir::Expr, callee: &hir::Expr) {
let callee_ty = return_if_err!(self.mc.expr_ty_adjusted(callee));
debug!("walk_callee: callee={:?} callee_ty={:?}",
callee, callee_ty);
match callee_ty.sty {
ty::FnDef(..) | ty::FnPtr(_) => {
self.consume_expr(callee);
}
ty::Error => { }
_ => {
if let Some(def_id) = self.mc.tables.type_dependent_def_id(call.hir_id) {
let call_scope = region::Scope {
id: call.hir_id.local_id,
data: region::ScopeData::Node
};
match OverloadedCallType::from_method_id(self.tcx(), def_id) {
FnMutOverloadedCall => {
let call_scope_r = self.tcx().mk_region(ty::ReScope(call_scope));
self.borrow_expr(callee,
call_scope_r,
ty::MutBorrow,
ClosureInvocation);
}
FnOverloadedCall => {
let call_scope_r = self.tcx().mk_region(ty::ReScope(call_scope));
self.borrow_expr(callee,
call_scope_r,
ty::ImmBorrow,
ClosureInvocation);
}
FnOnceOverloadedCall => self.consume_expr(callee),
}
} else {
self.tcx().sess.delay_span_bug(call.span,
"no type-dependent def for overloaded call");
}
}
}
}
fn walk_stmt(&mut self, stmt: &hir::Stmt) {
match stmt.node {
hir::StmtKind::Local(ref local) => {
self.walk_local(&local);
}
hir::StmtKind::Item(_) => {
// We don't visit nested items in this visitor,
// only the fn body we were given.
}
hir::StmtKind::Expr(ref expr) |
hir::StmtKind::Semi(ref expr) => {
self.consume_expr(&expr);
}
}
}
fn walk_local(&mut self, local: &hir::Local) {
match local.init {
None => {
local.pat.each_binding(|_, hir_id, span, _| {
self.delegate.decl_without_init(hir_id, span);
})
}
Some(ref expr) => {
// Variable declarations with
// initializers are considered
// "assigns", which is handled by
// `walk_pat`:
self.walk_expr(&expr);
let init_cmt = Rc::new(return_if_err!(self.mc.cat_expr(&expr)));
self.walk_irrefutable_pat(init_cmt, &local.pat);
}
}
}
/// Indicates that the value of `blk` will be consumed, meaning either copied or moved
/// depending on its type.
fn walk_block(&mut self, blk: &hir::Block) {
debug!("walk_block(blk.hir_id={})", blk.hir_id);
for stmt in &blk.stmts {
self.walk_stmt(stmt);
}
if let Some(ref tail_expr) = blk.expr {
self.consume_expr(&tail_expr);
}
}
fn walk_struct_expr(&mut self,
fields: &[hir::Field],
opt_with: &Option<P<hir::Expr>>) {
// Consume the expressions supplying values for each field.
for field in fields {
self.consume_expr(&field.expr);
}
let with_expr = match *opt_with {
Some(ref w) => &**w,
None => { return; }
};
let with_cmt = Rc::new(return_if_err!(self.mc.cat_expr(&with_expr)));
// Select just those fields of the `with`
// expression that will actually be used
match with_cmt.ty.sty {
ty::Adt(adt, substs) if adt.is_struct() => {
// Consume those fields of the with expression that are needed.
for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() {
let is_mentioned = fields.iter().any(|f| {
self.tcx().field_index(f.hir_id, self.mc.tables) == f_index
});
if !is_mentioned {
let cmt_field = self.mc.cat_field(
&*with_expr,
with_cmt.clone(),
f_index,
with_field.ident,
with_field.ty(self.tcx(), substs)
);
self.delegate_consume(with_expr.hir_id, with_expr.span, &cmt_field);
}
}
}
_ => {
// the base expression should always evaluate to a
// struct; however, when EUV is run during typeck, it
// may not. This will generate an error earlier in typeck,
// so we can just ignore it.
if !self.tcx().sess.has_errors() {
span_bug!(
with_expr.span,
"with expression doesn't evaluate to a struct");
}
}
}
// walk the with expression so that complex expressions
// are properly handled.
self.walk_expr(with_expr);
}
// Invoke the appropriate delegate calls for anything that gets
// consumed or borrowed as part of the automatic adjustment
// process.
fn walk_adjustment(&mut self, expr: &hir::Expr) {
let adjustments = self.mc.tables.expr_adjustments(expr);
let mut cmt = return_if_err!(self.mc.cat_expr_unadjusted(expr));
for adjustment in adjustments {
debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
match adjustment.kind {
adjustment::Adjust::NeverToAny |
adjustment::Adjust::Pointer(_) => {
// Creating a closure/fn-pointer or unsizing consumes
// the input and stores it into the resulting rvalue.
self.delegate_consume(expr.hir_id, expr.span, &cmt);
}
adjustment::Adjust::Deref(None) => {}
// Autoderefs for overloaded Deref calls in fact reference
// their receiver. That is, if we have `(*x)` where `x`
// is of type `Rc<T>`, then this in fact is equivalent to
// `x.deref()`. Since `deref()` is declared with `&self`,
// this is an autoref of `x`.
adjustment::Adjust::Deref(Some(ref deref)) => {
let bk = ty::BorrowKind::from_mutbl(deref.mutbl);
self.delegate.borrow(expr.hir_id, expr.span, &cmt, deref.region, bk, AutoRef);
}
adjustment::Adjust::Borrow(ref autoref) => {
self.walk_autoref(expr, &cmt, autoref);
}
}
cmt = return_if_err!(self.mc.cat_expr_adjusted(expr, cmt, &adjustment));
}
}
/// Walks the autoref `autoref` applied to the autoderef'd
/// `expr`. `cmt_base` is the mem-categorized form of `expr`
/// after all relevant autoderefs have occurred.
fn walk_autoref(&mut self,
expr: &hir::Expr,
cmt_base: &mc::cmt_<'tcx>,
autoref: &adjustment::AutoBorrow<'tcx>) {
debug!("walk_autoref(expr.hir_id={} cmt_base={:?} autoref={:?})",
expr.hir_id,
cmt_base,
autoref);
match *autoref {
adjustment::AutoBorrow::Ref(r, m) => {
self.delegate.borrow(expr.hir_id,
expr.span,
cmt_base,
r,
ty::BorrowKind::from_mutbl(m.into()),
AutoRef);
}
adjustment::AutoBorrow::RawPtr(m) => {
debug!("walk_autoref: expr.hir_id={} cmt_base={:?}",
expr.hir_id,
cmt_base);
// Converting from a &T to *T (or &mut T to *mut T) is
// treated as borrowing it for the enclosing temporary
// scope.
let r = self.tcx().mk_region(ty::ReScope(
region::Scope {
id: expr.hir_id.local_id,
data: region::ScopeData::Node
}));
self.delegate.borrow(expr.hir_id,
expr.span,
cmt_base,
r,
ty::BorrowKind::from_mutbl(m),
AutoUnsafe);
}
}
}
fn arm_move_mode(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm) -> TrackMatchMode {
let mut mode = Unknown;
for pat in &arm.pats {
self.determine_pat_move_mode(discr_cmt.clone(), &pat, &mut mode);
}
mode
}
fn walk_arm(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm, mode: MatchMode) {
for pat in &arm.pats {
self.walk_pat(discr_cmt.clone(), &pat, mode);
}
if let Some(hir::Guard::If(ref e)) = arm.guard {
self.consume_expr(e)
}
self.consume_expr(&arm.body);
}
/// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
/// let binding, and *not* a match arm or nested pat.)
fn walk_irrefutable_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat) {
let mut mode = Unknown;
self.determine_pat_move_mode(cmt_discr.clone(), pat, &mut mode);
let mode = mode.match_mode();
self.walk_pat(cmt_discr, pat, mode);
}
/// Identifies any bindings within `pat` and accumulates within
/// `mode` whether the overall pattern/match structure is a move,
/// copy, or borrow.
fn determine_pat_move_mode(&mut self,
cmt_discr: mc::cmt<'tcx>,
pat: &hir::Pat,
mode: &mut TrackMatchMode) {
debug!("determine_pat_move_mode cmt_discr={:?} pat={:?}", cmt_discr, pat);
return_if_err!(self.mc.cat_pattern(cmt_discr, pat, |cmt_pat, pat| {
if let PatKind::Binding(..) = pat.node {
let bm = *self.mc.tables.pat_binding_modes()
.get(pat.hir_id)
.expect("missing binding mode");
match bm {
ty::BindByReference(..) =>
mode.lub(BorrowingMatch),
ty::BindByValue(..) => {
match copy_or_move(&self.mc, self.param_env, &cmt_pat, PatBindingMove) {
Copy => mode.lub(CopyingMatch),
Move(..) => mode.lub(MovingMatch),
}
}
}
}
}));
}
/// The core driver for walking a pattern; `match_mode` must be
/// established up front, e.g., via `determine_pat_move_mode` (see
/// also `walk_irrefutable_pat` for patterns that stand alone).
fn walk_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat, match_mode: MatchMode) {
debug!("walk_pat(cmt_discr={:?}, pat={:?})", cmt_discr, pat);
let tcx = self.tcx();
let ExprUseVisitor { ref mc, ref mut delegate, param_env } = *self;
return_if_err!(mc.cat_pattern(cmt_discr.clone(), pat, |cmt_pat, pat| {
if let PatKind::Binding(_, canonical_id, ..) = pat.node {
debug!(
"walk_pat: binding cmt_pat={:?} pat={:?} match_mode={:?}",
cmt_pat,
pat,
match_mode,
);
if let Some(&bm) = mc.tables.pat_binding_modes().get(pat.hir_id) {
debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm);
// pat_ty: the type of the binding being produced.
let pat_ty = return_if_err!(mc.node_ty(pat.hir_id));
debug!("walk_pat: pat_ty={:?}", pat_ty);
// Each match binding is effectively an assignment to the
// binding being produced.
let def = Res::Local(canonical_id);
if let Ok(ref binding_cmt) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) {
delegate.mutate(pat.hir_id, pat.span, binding_cmt, MutateMode::Init);
}
// It is also a borrow or copy/move of the value being matched.
match bm {
ty::BindByReference(m) => {
if let ty::Ref(r, _, _) = pat_ty.sty {
let bk = ty::BorrowKind::from_mutbl(m);
delegate.borrow(pat.hir_id, pat.span, &cmt_pat, r, bk, RefBinding);
}
}
ty::BindByValue(..) => {
let mode = copy_or_move(mc, param_env, &cmt_pat, PatBindingMove);
debug!("walk_pat binding consuming pat");
delegate.consume_pat(pat, &cmt_pat, mode);
}
}
} else {
tcx.sess.delay_span_bug(pat.span, "missing binding mode");
}
}
}));
// Do a second pass over the pattern, calling `matched_pat` on
// the interior nodes (enum variants and structs), as opposed
// to the above loop's visit of than the bindings that form
// the leaves of the pattern tree structure.
return_if_err!(mc.cat_pattern(cmt_discr, pat, |cmt_pat, pat| {
let qpath = match pat.node {
PatKind::Path(ref qpath) |
PatKind::TupleStruct(ref qpath, ..) |
PatKind::Struct(ref qpath, ..) => qpath,
_ => return
};
let res = mc.tables.qpath_res(qpath, pat.hir_id);
match res {
Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_did) => {
let variant_did = mc.tcx.parent(variant_ctor_did).unwrap();
let downcast_cmt = mc.cat_downcast_if_needed(pat, cmt_pat, variant_did);
debug!("variantctor downcast_cmt={:?} pat={:?}", downcast_cmt, pat);
delegate.matched_pat(pat, &downcast_cmt, match_mode);
}
Res::Def(DefKind::Variant, variant_did) => {
let downcast_cmt = mc.cat_downcast_if_needed(pat, cmt_pat, variant_did);
debug!("variant downcast_cmt={:?} pat={:?}", downcast_cmt, pat);
delegate.matched_pat(pat, &downcast_cmt, match_mode);
}
Res::Def(DefKind::Struct, _)
| Res::Def(DefKind::Ctor(..), _)
| Res::Def(DefKind::Union, _)
| Res::Def(DefKind::TyAlias, _)
| Res::Def(DefKind::AssocTy, _)
| Res::SelfTy(..) => {
debug!("struct cmt_pat={:?} pat={:?}", cmt_pat, pat);
delegate.matched_pat(pat, &cmt_pat, match_mode);
}
_ => {}
}
}));
}
fn walk_captures(&mut self, closure_expr: &hir::Expr, fn_decl_span: Span) {
debug!("walk_captures({:?})", closure_expr);
let closure_def_id = self.tcx().hir().local_def_id(closure_expr.hir_id);
if let Some(upvars) = self.tcx().upvars(closure_def_id) {
for (&var_id, upvar) in upvars.iter() {
let upvar_id = ty::UpvarId {
var_path: ty::UpvarPath { hir_id: var_id },
closure_expr_id: closure_def_id.to_local(),
};
let upvar_capture = self.mc.tables.upvar_capture(upvar_id);
let cmt_var = return_if_err!(self.cat_captured_var(closure_expr.hir_id,
fn_decl_span,
var_id));
match upvar_capture {
ty::UpvarCapture::ByValue => {
let mode = copy_or_move(&self.mc,
self.param_env,
&cmt_var,
CaptureMove);
self.delegate.consume(closure_expr.hir_id, upvar.span, &cmt_var, mode);
}
ty::UpvarCapture::ByRef(upvar_borrow) => {
self.delegate.borrow(closure_expr.hir_id,
fn_decl_span,
&cmt_var,
upvar_borrow.region,
upvar_borrow.kind,
ClosureCapture(upvar.span));
}
}
}
}
}
fn cat_captured_var(&mut self,
closure_hir_id: hir::HirId,
closure_span: Span,
var_id: hir::HirId)
-> mc::McResult<mc::cmt_<'tcx>> {
// Create the cmt for the variable being borrowed, from the
// perspective of the creator (parent) of the closure.
let var_ty = self.mc.node_ty(var_id)?;
self.mc.cat_res(closure_hir_id, closure_span, var_ty, Res::Local(var_id))
}
}
fn copy_or_move<'a, 'tcx>(
mc: &mc::MemCategorizationContext<'a, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
cmt: &mc::cmt_<'tcx>,
move_reason: MoveReason,
) -> ConsumeMode {
if !mc.type_is_copy_modulo_regions(param_env, cmt.ty, cmt.span) {
Move(move_reason)
} else {
Copy
}
}
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